1. Field of the Invention
This invention is directed to magnetic material structures, methods for making magnetic material structures and devices made from magnetic material structures.
2. Description of the Prior Art
As the home, office, transportation system, business place and factory become more automated and electronically connected, and as electronic devices and appliances such as computers, communication devices, wireless communication devices, electronic games, entertainment systems, personal data assistants, transportation vehicles, manufacturing tools, shop tools, and home appliances become more sophisticated there is, and will be, an ever-increasing demand for higher performance and low cost electronic circuits, sensors, transducers, data storage systems and other magnetic devices which employ magnetic thin film materials. In order for these devices to remain competitive in the market place each product generation must be higher performing, unobtrusive and, usually, less expensive than the previous. Hence there are ever increasing demands for technical improvements in the materials and structure of these devices.
For all of these applications the magnetic material has an improved performance if the magnetic properties can be better controlled during the construction. Two familiar properties, which are sometimes considered to be intrinsic magnetic properties, are the saturation magnetization, Ms, and the magnetocrystalline anisotropy energy density constants (usually denoted by a subscripted K symbol). The meaning of magnetic anisotropy energy is that the magnetization would have a preferred direction, or directions, of orientation. That is, the energy of the system is minimal when the magnetization vector points along certain directions. These directions are referred to as the magnetic easy axes while the magnetic hard axes coincide with magnetic orientations where the energy is maximized. However, it should be noted that the magnetic anisotropy is not actually an intrinsic property in the sense that the materials are commonly not made perfectly. Nevertheless, good performance in device applications is almost always dependent upon there being a single preferred magnetic orientation or anisotropy direction and so in the manufacturing process one strives to achieve a desired uniaxial anisotropy. An objective of the present invention is to provide new mechanisms for controlling the magnetocrystalline anisotropy of thin magnetic films. By doing so the performance of almost all magnetic devices are envisioned to be improved.
In general the anisotropy energy is a function of the orientation of the magnetization vector with respect to a given physical axis. Here, we define a “uniaxial” anisotropy to exist if the anisotropy energy density function only contains a single maximum and a single minimum as the magnetization angle, θ, is rotated by 180 degrees from a physical axis. Likewise we define an “ideal uniaxial” anisotropy energy to exist if the energy equation has only a sin2(θ) or cos2(θ) dependence. Materials and device processing to achieve a desired orientation or anisotropy is commonly difficult and sometimes impossible, perhaps because heretofore the mechanism for achieving anisotropic orientation has not been well understood. Furthermore, uniform control of the orientation of the magnetic anisotropy is often difficult to achieve and maintain in a manufacturing process where many different desired material properties must be obtained simultaneously.